Cooling system with controlled biphase mixing of refrigerant

ABSTRACT

A method for cooling with a refrigerant based cooling system includes circulating a refrigerant in a main flow path of a refrigeration cycle including an accumulator, compressor, condenser and an evaporator, diverting a portion of flow to a bypass flow path from a location along the main flow path that is downstream the compressor and upstream the condenser and combining flow through the bypass flow path with flow through the main flow path downstream the condenser and upstream from the evaporator. The rate of flow through the bypass flow path may be dynamically controlled.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to abi-phase refrigerant based cooling system and, more particularly, butnot exclusively, to a temperature forcing system for coolingsemiconductor components under test.

Air conditioning units and refrigerators are example cooling systemscommonly found in most households. The basic operation of such coolingsystems includes circulating a refrigerant between a compressor,condenser, expansion valve and an evaporator. In some systems, thecompressor is operated at a constant speed and temperature of thecooling system is regulated by turning the compressor OFF whenever adesired temperature is reached and then turning the compressor back ONwith a threshold rise in temperature. The compressor may typically bethe main power consuming component in the system. Other more advancedsystems include inverter compressors that operate at variable speed.Operating the compressor at variable speed reduces the frequency atwhich compressor is required to be turned OFF/ON and also facilitates inoperating the compressor at variable capacity. In this manner, powerefficiency may be increased and noise level may be reduced. Furthermore,relatively fast cooling may be achieved by initially operating theinverter compressor at full capacity to reach a desired temperature andthen significantly reducing the capacity to maintain that temperature.Drawbacks associated with inverter compressors includes increased costof manufacture and mechanical complexity. Although, inverter compressorsdo provide some advantages, the need for cooling systems with improvedcost efficiency, improved power efficiency and/or reduced noise is stilla sought after goal.

A temperature forcing system is another example cooling system that isused to controllably cool semiconductor devices (chips or modules) undertest. During the testing procedure, the temperature forcing system maysubject a device under test (DUT) to range of temperatures over whichthe DUT may be configured to be operable or to extreme temperaturevalues of its working range. Example extreme values may be between 125°C. and 165° C., at a high end of the working range, and between −40° C.and −70° C., at a low end of the working range. During operation, theDUT is also expected to generate heat. Precise temperature regulation istypically required to reach and maintain DUT in each of the desiredtemperatures even in the face of heat being generated by the DUT.

U.S. Pat. No. 9,677,822, entitled “Efficient temperature forcing ofsemiconductor devices under test,” the contents of which is incorporatedby reference herein discloses a temperature-forcing system and method,for controlling the temperature of an electronic device under test(DUT). The system is disclosed to include a refrigerant circulationsubsystem that circulates bi-phase refrigerant, in closed loop fashion,through an evaporator so that, during circulation, said refrigerant ismaintained at high pressure between a compressor and a metering deviceof the subsystem and at low pressure while flowing through theevaporator. The system additionally includes a plunger that isconfigured to physically contact a casing of the DUT and thereby formthermal contact between the DUT and the evaporator of the system.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present inventionthere is provided a refrigerant based cooling system with improvedtemperature regulation. According to some example embodiments, thecooling system is configured to regulate temperature based ondynamically controlling a ratio between gas and liquid refrigerantentering an evaporator of the cooling system. According to some exampleembodiments, the cooling system includes dedicated flow paths for eachof the liquid and gas phase of the refrigerant and a mixing chamber inwhich the liquid and gas refrigerant may be mixed at the desired ratio.The gas refrigerant may be gas exiting the compressor at a hightemperature. During operation, the evaporator may for example be fedwith a relatively high ratio of gas to liquid when little or no activecooling is desired, and may be fed with a relatively low ratio of gas toliquid when high or maximum active cooling is desired. The presentinventors have found that high accuracy temperature regulation as wellas rapid changes in temperature may be achieved over relatively largeworking ranges based on the system and method described herein.Optionally, temperature may be regulated with an accuracy of up to 0.1°C.-1° C., e.g. 0.5° C.

The cooling system as described herein may also be cost efficient inthat the improved temperature regulation may be achieved withoutadditional moving parts or complex mechanical elements. In some exampleembodiments, the temperature regulation may be achieved while runningthe compressor at a steady speed and/or without turning the compressorON/OFF during operation of the cooling system. When running thecompressor at a steady speed, the cooling system may be operated withimproved power efficiency and reduced noise.

In some example embodiments, the cooling system is configured fortemperature forcing of electronic components under test and may providefast changes in temperature with precise temperature regulation over alarge working range. In other example embodiments, the cooling systemmay be adapted to control the temperature of other solid bodies orfluids and may be integrated in other systems including air conditioning(AC) systems and refrigerators.

According to an aspect of some example embodiments, there is provided amethod for cooling with a refrigerant based cooling system, the methodcomprising: circulating a refrigerant in a main flow path of arefrigeration cycle including an accumulator, compressor, condenser andan evaporator; diverting a portion of flow to a bypass flow path from alocation along the main flow path that is downstream the compressor andupstream the condenser; dynamically controlling rate of flow through thebypass flow path; and combining flow through the bypass flow path withflow through the main flow path downstream the condenser and upstreamfrom the evaporator.

Optionally, the flow through the bypass flow path and the flow throughthe main flow path is combined in a dedicated mixing chamber, whereinthe mixing chamber is integrated in the main flow path downstream fromthe condenser and upstream from the evaporator.

Optionally, the portion of flow that is diverted to the bypass flow pathis flow of the refrigerant in a gaseous phase.

Optionally, the refrigerant upstream from the bypass flow path isbi-phasic refrigerant and wherein the method further comprises:separating a liquid refrigerant from a vaporized refrigerant; directingthe liquid refrigerant to the condenser via the main flow path; anddiverting at least a portion of the vaporized refrigerant to the bypassflow path.

Optionally, the refrigerant upstream from the bypass flow path is fullyvaporized.

Optionally, the method includes sensing a cooling effect of the coolingsystem and adjusting the rate of refrigerant flow through the bypassflow path based on the cooling effect that is sensed.

Optionally, the method includes cooling refrigerant flowing through thecondenser based on heat exchange with a second refrigeration cycle thatis thermally coupled with the condenser.

Optionally, the main flow path is configured to branch out into aplurality of sub-flow paths downstream from the condenser, and whereinrefrigerant flowing in each of the plurality sub-flow paths feeds intoone of a plurality of evaporators and wherein the refrigerant flowing inthe plurality of evaporators is collected by the accumulator.

Optionally, the bypass flow path is configured to branch out into aplurality of sub-bypass flow paths, wherein flow rate of refrigerantthough each of the plurality of sub-bypass flow paths is separatelycontrolled.

Optionally, vaporized refrigerant from each of the plurality ofsub-bypass flow paths is combined with liquid refrigerant in one of theplurality of sub-flow paths of the main flow path.

According to an aspect of some example embodiments, there is provided acooling system comprising: a refrigerant; an accumulator, a compressor,a condenser and an evaporator fluidly connected by a main flow pathconfigured to circulate refrigerant therein; a bypass flow pathconfigured to divert a portion of flow from a location on the main flowpath that is downstream the compressor and upstream the condenser; avalve configured to control flow through the bypass flow path; a mixingchamber configured to receive refrigerant from both the main flow pathand the bypass flow path and to direct outflow from the mixing chamberto the evaporator; and a controller configured to dynamically controloperation of the valve.

Optionally, the mixing chamber comprises: a first inlet configured toreceive flow from a location along the main flow path that is downstreamthe condenser and upstream from the evaporator; a second inletconfigured to receive flow from the bypass flow path; and an outletconfigured to direct flow from one or more of the first inlet and thesecond inlet to the evaporator.

Optionally, outflow from the mixing chamber is through a tube includingan open tip penetrating within the mixing chamber, wherein the tip ispositioned at a defined height within the mixing chamber.

Optionally, the tube is integral to a metering device providing flowcommunication between the mixing chamber and the evaporator.

Optionally, the tube is a capillary tube.

Optionally, the mixing chamber is elongated in a vertical direction andwherein the first inlet is positioned below the second inlet.

Optionally, the portion of flow through the bypass flow path is gaseousflow.

Optionally, the cooling system includes a vapor-liquid separatorintegrated into the main flow path downstream from the compressor andconfigured to direct flow to the bypass flow path.

Optionally, the vapor-liquid separator is configured to receive bi-phaserefrigerant from the compressor and to separately direct liquidrefrigerant to the condenser and at least a portion of the vaporizedrefrigerant to the bypass flow path.

Optionally, the cooling system includes a flow splitter configured todivide outflow from the compressor between the main flow path and thebypass flow path.

Optionally, the refrigerant upstream the flow splitter is fullyvaporized.

Optionally, the cooling system includes a sensor configured to sense acooling effect of the cooling system, wherein the controller isconfigured to receive input from the sensor and to regulate the valvebased on the input.

Optionally, the cooling system includes an additional refrigerationcycle separate from the main flow path and thermally coupled to thecondenser, wherein the additional refrigeration cycle is configured coolrefrigerant in the main flow path.

Optionally, the cooling system includes a plurality of evaporators andwherein refrigerant from the plurality of evaporators is collected bythe accumulator.

Optionally, the cooling system includes a plurality of sub-bypass flowpaths, each branching out from the bypass flow path; a plurality ofvalves, each of the plurality of valves configured to control flowthrough one of the plurality of sub-bypass flow paths; and a pluralityof mixing chambers, each of the plurality of mixing chambers configuredto receive refrigerant from both the main flow path and one of theplurality of sub-bypass flow path and to direct outflow from the mixingchamber to one of the plurality of evaporators.

Optionally, the controller is configured to separately control each ofthe plurality of valves.

Optionally, the cooling system includes a plurality of sensors, eachconfigured to sense a cooling effect based on one of the plurality ofevaporators, wherein the controller is configured to regulate theplurality of valves based on input from the plurality of sensors.

According to an aspect of some example embodiments, there is provided amixing chamber integrated in a refrigeration cycle, the mixing chambercomprising: a housing having an elongated shape along a verticaldirection; a first inlet configured to receive condensed liquidrefrigerant from a main flow path of a refrigeration cycle; a secondinlet configured to receive vaporized refrigerant expelled from acompressor of the refrigeration cycle; and an outlet port configured todirect flow from one or more of the first inlet and the second inlet toan evaporator of the refrigeration cycle.

Optionally, the mixing chamber includes a tube extending through theoutlet and configured to extend vertically within the housing at adefined height, wherein flow out of the chamber is configured to flowthrough the tube.

Optionally, the tube extends out of the mixing chamber and is integralto a metering device of the refrigeration cycle.

Optionally, the tube is a capillary tube.

Optionally, an open end of the tube within the mixing chamber is angled.

Optionally, an open end of the tube within the mixing chamber isperforated.

Optionally, an open end of the tube within the mixing chamber is coveredwith a porous material.

Optionally, the first inlet is positioned below the second inlet.

Optionally, the outlet is through a floor or base of the housing.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified block diagram of an example single looprefrigeration cycle in accordance with some example embodiments;

FIGS. 2A and 2B are simplified schematic drawings showing flow throughan example mixing chamber while a gas flow control valve of therefrigeration cycle is open and closed respectively, both in accordancewith some example embodiments;

FIGS. 3A and 3B are perspective and cross sectional views respectivelyof an example mixing chamber, both in accordance with some exampleembodiments;

FIGS. 4A, 4B and 4C are example structural variations for an inlet intoa tube extending into the mixing chamber and directing flow into theevaporator, all in accordance with some embodiments;

FIG. 5 is a schematic drawing of an example gas-liquid separator inaccordance with some example embodiments;

FIG. 6 is a simplified block diagram of an example dual looprefrigeration cycle in accordance with some example embodiments;

FIG. 7 is a simplified block diagram of an example single looprefrigeration cycle including a plurality of separately controlledevaporators in accordance with some example embodiments;

FIG. 8 is a simplified block diagram of an example double looprefrigeration cycle including a plurality of separately controlledevaporators in accordance with some example embodiments;

FIG. 9 is a simplified flow chart of an example method to regulatetemperature in accordance with some example embodiments;

FIG. 10 is a perspective view of an example temperature forcing systemincluding an example double loop refrigeration cycle in accordance withsome example embodiments; and

FIGS. 11A, 11B and 11C are three example configurations for integratinga heating coil on a temperature forcing plate in accordance with someexample embodiments.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to abi-phase refrigerant based cooling system and, more particularly, butnot exclusively, to a temperature forcing system for coolingsemiconductor components under test.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

According to some example embodiments, a refrigerant based coolingsystem includes, as part of a refrigeration cycle, separated flow pathsfor the refrigerant in each of a liquid and a gas phase and a mixingchamber configured to merge or mix the flow from the separated flowpaths. According to some example embodiments, the refrigerant issupplied to both flow paths from a common compressor. Outflow from themixing chamber may be fed into an evaporator through a metering devicesuch as for example an expansion valve or, preferably, a capillary tube.According to some example embodiments, the gas and liquid refrigerant isconfigured to flow into the mixing chamber in a desired relativeproportion that may be dynamically controlled. Optionally andpreferably, the dynamic control is provided based on controlling a flowrate of the gas refrigerant into the mixing chamber. The desiredrelative proportion may be a desired volume ratio of gas to liquid.Optionally, flow rate of one or more of the gas and liquid into themixing chamber may be controlled to obtain the desired relativeproportion. In some example embodiments, the gas phase flow pathincludes a flow control valve and flow rate of gas is controlled withthe flow control valve while the liquid passively flows into the mixingchamber based on the pressure level established with the flow controlvalve. The gas in the gas flow path is hot gas diverted from the mainflow cycle. In some example embodiments, a controller of the coolingsystem is configured to control the flow control valve based on inputfrom a user interface and/or output from one or more sensors, e.g.temperature sensors associated with the cooling system.

According to some example embodiments, temperature is regulated based onselectively altering a proportion of gas and liquid in the mixturesupplied to the evaporator from the mixing chamber. By adjusting the gasflow control valve, the mixing chamber may be filled with gas and liquidin varying proportions. For example, a mixture that is predominatelyliquid may provide more cooling as compared to mixture that ispredominately gas. Optionally, maximum cooling may be initiated based onclosing the gas flow control valve and thereby allowing only liquidrefrigerant to flow into the mixing chamber. Optionally, minimum coolingor no cooling may occur based on opening the flow control valve to amaximum working flow and thereby allowing only gas refrigerant to flowinto the mixing chamber.

According to some example embodiments, the mixing chamber includesdedicated inlet ports for each of the liquid and gas flow paths and anoutlet port from which the mixed flow is directed through a meteringdevice to an evaporator. According to some example embodiments, a tubehaving an open end extends through the outlet port and is positionedwith the open end at a defined height in the mixing chamber. On anopposite end, the tube may be coupled to a metering device through whichthe liquid and gas in the mixing chamber flows into the evaporator. Insome example embodiments, the mixing chamber is configured to have anelongated shape extending in a vertical direction. Optionally, the gasinlet port is positioned on an upper half of the mixing chamber and theliquid inlet port is positioned on a lower half of the mixing chamber.In some example embodiments, the outlet port at a base or floor of themixing chamber is configured to receive a tube penetrating therethroughin a vertical direction. In this configuration, a height of the tube mayoptionally be adjusted, e.g. during a calibration procedure.Alternatively, the tube may penetrate through a side wall of the mixingchamber at a defined height. The open end or inlet of the tube may havedifferent structural configurations. Optionally, the open end may beangled, may be perforated along a portion of its height and/or may becovered with an element that partially restricts flow into the open end.

In some example embodiments, the cooling system includes a vapor-liquidseparator configured to divide outflow from a compressor into separatedflow paths for liquid and gas. In some example embodiments, thevapor-liquid separator is a chamber including a liquid outlet at abottom portion of the chamber and a vapor outlet at an upper portion ofthe chamber. The liquid and gas may be separated based on gravity.Optionally, an inlet to the vapor-liquid separator is also at an upperportion of the chamber.

In other example embodiments, output from the compressor is configuredto be entirely in a gaseous phase, due for example to the type ofrefrigerant used, e.g. one with an essentially low boiling temperature,and therefore a vapor-gas separator may not be required. Instead, afilter or flow splitter may direct a first portion of the gas flow tothe dedicated gas flow path and a second portion of the flow to the mainbranch, wherein a condenser (being part of a heat exchanger) may serveto liquefy the refrigerant. Optionally, the cooling system includes adual cycle, with one of the cycles being dedicated to generating theliquid phase for the other cycle. Optionally, lower temperature may bereached with the dual cycle system as compared to a single cycle system.

According to some example embodiments, a cooling system may includemultiple evaporators. Optionally, one or more of the evaporators may beindividually controlled. For example, one or more of the evaporators maybe associated with a dedicated mixing chamber, and flow control valvefor controlling flow into the dedicated mixing chamber. Optionally, oneor more of the evaporators is additionally associated with a dedicatedtemperature sensor based on which temperature may be regulated.

Reference is now made to FIG. 1 showing a simplified block diagram of anexample single loop refrigeration cycle in accordance with some exampleembodiments. According to some example embodiments, a refrigerationcycle 100 may be similar to conventional refrigeration cycle in thatrefrigeration cycle 100 is configured to circulate a bi-phaserefrigerant from an accumulator 20, through a compressor 30, a condenser40, optionally and preferably a dryer 50, a metering device 60 and anevaporator 70, and then back to accumulator 20. Optionally andpreferably accumulator 20 is a suction accumulator. Optionally andpreferably metering device 60 is a capillary tube. Cooling of a body ora flow of air may be provided by evaporator 70 when thermally coupled bydirect or indirect coupling to the body or a flow of air. A controller10 controls operation of refrigeration cycle and may receive input fromone or more sensors 90 and adjust cooling parameters based on inputreceived from one or more sensors 90. Sensor 90 may be a temperaturesensor, e.g. thermostat or thermocouple positioned on or near evaporator70 or on the body that is to be cooled. Controller 10 may also includeor be associated with a user interface configured to receive commandsfrom a user operating the cooling system. Refrigeration cycle 100together with controller 10 form an example cooling system. Sensors 90when present may also be part of the cooling system.

According to some example embodiments, refrigeration cycle 100 isconfigured to direct, e.g. divert at least a portion of refrigerant gasflow downstream from compressor 30 through a dedicated bypass flow path316 that bypasses condenser 40 and optionally and preferably dryer 50.Dedicated flow path 316 includes a valve 300 that is configured tocontrol the flowrate therethough and thereby controllably reintroducerefrigerant gas in flow path 316 into a main flow path 314 of coolingsystem 100 downstream from a condenser 40 and dryer 50 when present andupstream from evaporator 70. Valve 300 may be controllably operated withcontroller 10. In some example embodiments, valve 300 is anoff-the-shelf component that is configured to controllably regulate gasflow. According to some example embodiments, a mixing chamber 400integrated in main flow path 314 is configured to receive bothrefrigerant gas flow from dedicated flow path 316 and refrigerant liquidflow from condenser 40 and/or dryer 50 and feed or direct the combinedflow into metering device 60.

According to some example embodiments, refrigeration cycle 100additionally includes a vapor-liquid separator 310 downstream fromcompressor 30 and upstream condenser 40. Vapor-liquid separator 310 isconfigured to divert from main flow path 314 refrigerant in purelygaseous phase into bypass flow path 316.

In operation, accumulator 20 draws in gas and/or a mixture of gas aliquid from evaporator 70. Optionally, the gas or mixture is suctionedout of evaporator 70. Suctioned flow is directed through compressor 30configured to compress the gas and/or the mixture. According to someexample embodiments, the compressed refrigerant (gas and/or mixture ofgas and liquid) is then split in vapor-liquid separator 310 into a mainflow path 314 toward compressor 40 and a bypass flow path 316. Bypassflow path 316 includes valve 300 and bypasses condenser 40 andoptionally dryer 50 when present. In some example embodiments,controller 10 dynamically controls opening and closing of valve 300 andthereby a gas flowrate therethrough. According to some exampleembodiments, liquid from condenser 40 and gas from flow path 316concurrently flow into mixing chamber 400 at variable proportions basedon positioning of valve 300. Optionally, output from condenser 40includes both liquid and gas. For example, while valve 300 is fullyopened, gas from flow path 316 may enter mixing chamber 400 at a highflowrate and push out liquid that would otherwise flow in from main flowpath 314, e.g. from condenser 40 and dryer 50. In another example, whilevalve 300 is closed, mixing chamber may only receive flow from main flowpath 314 with no gas from flow path 316 entering mixing chamber 400.According to some example embodiments, output from mixing chamber 400directs flow into metering device 60 and through evaporator 70. Thecooling effect afforded by evaporator 70 may depend on a proportion ofgas and liquid flowing into evaporator 70. A mixture includingproportionately more liquid (and less gas) may provide more cooling ascompared to a mixture including proportionately less liquid (and moregas). Temperature may be sensed with one or more sensors 90 andcontroller 10 may adjust opening of valve 10 based on input from one ormore sensors 90 to dynamically regulate the temperature.

According to some example embodiments, refrigeration cycle 100 providesa relatively fast temperature response due the ability to alter theproportion between gas and liquid on-the-fly. Typically, a coolingeffect provided the evaporator is directly related to the proportion ofliquid within the evaporator. By altering that proportion on the fly,the cooling rate provided by the evaporator may also be altered on thefly.

According to some example embodiments, during operation compressor 30may be configured to be operated at a constant rate regardless of thecooling rate and/or temperature that is desired to be obtained. Rather adesired cooling rate and/or temperature may be achieved based onaltering the proportion flow into evaporator 70, for example bycontrolling opening and closing of valve 300.

Reference is now made to FIGS. 2A and 2B schematically showing exampleflow through an example mixing chamber while gas flow control valve ofthe refrigeration cycle is open and closed respectively, both inaccordance with some example embodiments. According to some exampleembodiments, mixing chamber 400 includes a housing 490 with a liquidinlet port 420 fluidly connected to main flow path 314 configured toreceive liquid flow from condenser 40 (and optionally dryer 50), a gasinlet port 410 receiving gas flow from flow path 316 through which flowis regulated by controller 10 with valve 300, and an outlet port 430through which a tube 450 is introduced into a volume of housing 490.Outflow from mixing chamber 400 is through tube 450 with tube inlet 455and may be directed to evaporator 70 via a metering device. Optionally,tube 450 is integral to metering device 60 (FIG. 1). Optionally, tube450 is a capillary tube or is another tube fitted on a capillary tube.Diameter of tube 450 may be selected based on system requirements.Example diameters may be 0.1 mm to 10 mm.

Housing 490 may have an elongated shape with height L and tube inlet 455of tube 450 may be positioned within housing 490 at a defined heightX=0. Optionally, outlet port 430 is at a bottom portion of mixingchamber and tube 450 extends into housing 490 vertically through outletport 430 and is fixedly positioned with tube inlet 455 at height X=0.According to some example embodiments, a height ‘x’ of liquid inrelation to tube inlet 455 may be controlled by controlling opening ofvalve 300.

In one example extreme state shown in FIG. 2A, valve 300 may be fullyopened (i.e. providing minimal resistance to flow) and hot refrigerantin vapor state may flow at substantially full pressure supplied bycompressor 30 through gas inlet port 410 into mixing chamber 400.Concurrently, flow from main flow path 314 reaches mixing chamber at asubstantially lower pressure and temperature. The lower pressure is duefor example to a flow resistance through condenser 40 and optionallydryer 50 as well as due shrinkage in volume that results from thecondensation. In some example embodiments, the higher gas pressure maypush a level of liquid to a height X below tube inlet 455 in tube 450.In this example state, only gas would flow through tube 450 intoevaporator 70. Typically, pressure within mixing chamber 400 ismaintained at a steady pressure with a level of the liquid within mixingchamber 400 (height X) varying based on pressure from gas flowing intogas inlet port 410.

In another example extreme state shown in FIG. 2B, valve 300 is fullyclosed (i.e. has infinite resistance to flow) and substantially norefrigerant flows from flow path 316 and into gas inlet port 410.Instead, liquid flow (or a mix of liquid and gas) from main flow path314 may flow through liquid inlet port 420 and may substantially fillmixing chamber 400. Flow through liquid inlet port 420 may be free toflow in the absence of any counter pressure from gas flowing through gasinlet port 410. Liquid refrigerant in this case may rise to a height‘-x’ in relation to tube inlet 455 of tube 450. In this state, onlyliquid may flow into evaporator 70. While only liquid flows into theevaporator, cooling system 100 may operate in a manner that is similarto conventional cooling systems.

Generally there may be intermediate operational states, between theextreme states described above and corresponding to intermediate openingstates of flow control valve 300. In such states, gas flows throughbypass flow path 316 into gas inlet port 410 at a rate that is lowerthan the rate at which compressor 30 draws refrigerant throughevaporator 70 from the metering device 60 (FIG. 1). In such states, thepressure within mixing chamber 400 drops and liquid is drawn into themixing chamber 400 through liquid inlet port 420 until its level risesand reaches the level of tube inlet 455, at which point it may flowintermixed with the flowing gas into the tube 450 and evaporator 70. Aliquid flow rate is then automatically maintained such that, on theaverage, the total flow rate (i.e. the sum of the flow rates of gas andliquid) is determined by the action of the compressor, whereby theaverage pressure maintained within the mixing chamber keeps the level ofthe liquid at the level of tube inlet 455. Any change in the settings ofthe flow control level may cause a change in the gas flow rate, which inturn may cause an inverse change in the liquid flow rate—bringing abouta corresponding change in the proportion of liquid to gas in themetering device and the resulting change of the cooling effect in theevaporator.

For each intermediate state, as described above, there may occur shortterm limited variations in the flow rates, about the correspondingaverage values, which may be due to hydrodynamic instabilities,non-linear effects in the flow of liquid into the intake and boiling ofsome of the cool liquid upon contact with the hot gas-causing somebubbling.

The present inventors have found that when a height of the liquid is ator near a height of tube inlet 455, the liquid refrigerant undergoeslocal boiling which varies a proportion between the rates of flow ofliquid and vapor over time. The proportions may vary over time in anoscillatory or random pattern. The prevent inventors have found thatwhile the rates of flow of liquid and gas into tube inlet 455 may varydue to boiling, flow into the evaporator has an averaging affect and thecooling provided by the evaporator is substantially stable.

According to some example embodiments, a proportion between the rates offlow of liquid and vapor into tube 450 and into evaporator 70 may bedynamically regulated based on a desired cooling rate and/ortemperature. In some example embodiments, variable proportion betweenthe rates of flow of liquid and vapor into tube 450 is controlled basedon controlling a degree of opening of valve 300. The pressure applied bygas flowing into mixing chamber 400 sets a height X of liquid.

According to some example embodiments, the varying ratio between theflow rates of the cool liquid part and the hot gaseous part of therefrigerant, alters a ratio between cool liquid and hot gas and therebyan average temperature of the mixture flowing out of mixing chamber 400into evaporator 70 (via metering device 60). This variation intemperature may effect a cooling rate in the evaporator. Furthermore, asthis mixture enters evaporator 70, only the liquid part of the mixtureevaporates and extracts heat. As such the cooling effect and/or rate ofheat extraction by evaporator 70 may depend on the amount of liquid inthe mixture at any one time. Optionally, the dependence may be directlyproportional to amount of liquid in the mixture.

Reference is now made to FIGS. 3A and 3B showing perspective and a crosssectional views respectively of an example mixing chamber, both inaccordance with some example embodiments. According to some exampleembodiments, mixing chamber 400 includes housing 490, gas inlet port 410configured to receive gas from gas flow path 316 and liquid inlet port420 configured to receive liquid from main flow path 314 postcondensation. Valve actuator 405 controls flow of gas through gas inletport 410 into housing 490. According to some example embodiments, mixingchamber 400 additionally includes a tube 450, e.g. a capillary tube orother tube penetrating into housing 490 and providing a flow channel foroutflow from mixing chamber 400. According to some example embodiments,housing 490 is elongated in a vertical direction with liquid inlet port420 positioned in a bottom half of housing 490 and gas inlet 410positioned in an upper half of housing 490. Optionally, tube 450penetrates through a floor or base of housing 490 via an outlet port430. In other example embodiments, tube 450 may penetrate through a wallof housing 490 above the floor or base, e.g. tube 450 may penetratethrough a wall of housing 490 at height X=0.

Reference is now made to FIGS. 4A, 4B and 4C showing example structuralvariations for an inlet into a tube extending into the mixing chamberand directing flow into the evaporator, all in accordance with someembodiments. According to some example embodiments, tube inlet 455 at atip of tube 450 may be designed in different configurations. Optionally,a specified configuration may provide for improving stability and/orresponse speed of temperature regulation based on shorting the time overwhich variations in liquid/gas flow rates are averaged. In some exampleshown in FIG. 4A, tube inlet 455 may be angled for example in a definedangle, e.g. 45°. In other example embodiments, tube inlet 455 mayadditionally or alternatively include a plurality of perforations 457through which liquid and gas may flow. In yet another exampleembodiments, tube inlet 455 may be covered with a porous cover 458through which gas and liquid refrigerant may penetrate. In each case theheight of the liquid level at equilibrium may rise in correspondencewith the opening of valve 300, thus widening an aperture through whichthe liquid may flow into tube 450 and providing a more stable flow rate,e.g. with less short term fluctuations.

Reference is now made to FIG. 5 showing a schematic drawing of anexample gas-liquid separator in accordance with some exampleembodiments. In some example embodiments, refrigeration cycle 100(FIG. 1) includes a vapor-liquid separator 310. Optionally, vapor-liquidseparator 310 includes a housing 312 in which hot gas 320 and liquid 330from compressor 30 may flow via a bi-phase flow channel 31 extendingfrom compressor 30 into housing 312. Bi-phase refrigerant may collect inhousing 312 with liquid 330 settling at a bottom of housing 312 due togravity and gas 320 hovering above liquid 330. Optionally, a liquidoutlet 38 positioned at a base or bottom portion of housing 312 mayallow free flow of liquid 330 out of housing 312 and a gas outlet 39 atan upper portion, e.g. an upper half of housing 312 may direct gas flowthrough gas flow path 316. Flowrate of gas 320 may be controlled byvalve 300 (FIG. 1). Optionally, vapor-liquid separator 310 may include alevel sensor 340 configured to monitor a level of liquid in housing 312.Alternatively, level sensor 340 is not required. Optionally, liquidoutlet 38 may also be associated with a control valve configured tocontrollably restrict liquid flow out of housing 312.

Reference is now made to FIG. 6 showing a simplified block diagram of anexample dual loop refrigeration cycle in accordance with some exampleembodiments. According to some example embodiments, a wider range ofcooling temperatures including lower temperature cooling may be achievedwith a dual loop refrigeration cycle 200. Refrigeration cycle 200together with controller 10 form an example cooling system. Sensors 90when present may also be part of the cooling system. Dual looprefrigeration cycle 200 includes a first main refrigeration cycle 205that exchanges heat with an auxiliary refrigeration cycle 210. Auxiliaryrefrigeration cycle 210 may circulate a refrigerant between anaccumulator 25 configured to extract refrigerant from a heat exchanger,a compressor 35, an auxiliary cycle condenser 45, optionally a dryer 55,a metering device 65 and heat exchanger 80. Heat exchanger 80 may becoupled with an auxiliary cycle evaporator 75 through which secondrefrigerant of auxiliary refrigeration cycle 210 flows and a condenser40 through which first refrigerant of main refrigeration cycle 210flows. Heat exchanger 80 may exchange heat with main refrigeration cycle205 to extract heat and condense first refrigerant gas flowing in mainrefrigeration cycle 205. Optionally, second refrigerant in auxiliaryrefrigeration cycle 210 flows through dedicated auxiliary cycleevaporator 75 that is configured to exchange heat with condenser 40.Controller 10 may control operation of both auxiliary refrigerationcycle 210 and main refrigeration cycle 205 to achieve a desired coolingrate and temperature at evaporator 70 in main refrigeration cycle 205.

According to some example embodiments, main refrigeration cycle 205 isoperated with a first refrigerant that is configured to be in asubstantially gaseous phase when it flows out from the compressor due toits relatively low boiling temperature. The lower boiling temperatureprovides for achieving lower cooling temperatures. Since outflow fromcompressor 30 is in a gaseous phase, there is no need to separate liquidto create gas flow path 316. Instead, the vapor emerging from thecompressor passes through flow splitter or filter 320 that splits theflow path into a main flow path 314 and a bypass flow path 316.Optionally, the flow is split with approximately 50% flowing throughmain flow path 314 and 50% flowing through bypass flow path 316. Howeverother flow proportions may be contemplated. In some example embodiments,gas flow through main flow path 314 is condensed into a liquid phasethrough heat exchanger 80, while gas flow through flow path 316 ismaintained in its gaseous phase. Gas in flow path 316 may also be hotgas as it is received from compressor 30. In some example embodiments,gas flow through main flow path 314 may flow through a dedicatedcondenser that exchanges heat with heat exchanger 80. Optionally, heatexchanger 80 includes auxiliary cycle evaporator 75 through which secondrefrigerant from auxiliary refrigeration cycle 210 flows, condenser 40through which first refrigerant from main refrigeration cycle 205 flowsand thermal coupling therebetween configured to facilitate transfer ofheat from condenser 40 to auxiliary cycle evaporator 75.

According to some example embodiments, liquid from heat exchanger 80 andgas from flow path 316 is controllably combined in mixing chamber 400based on controlling valve 300 and the combined flow is directed tometering device 60 and auxiliary cycle evaporator 70 as described hereinabove. According to some example embodiments, a wider working range oftemperatures may be achieved based on dual loop refrigeration cycle. Forexample, highest temperature (minimum cooling) may be achieved whilevalve 300 is fully opened and evaporator 70 may be filled withrefrigerant in a gaseous state. Lowest temperature (maximum cooling) maybe achieved while valve 300 is closed and evaporator 70 is filled withrefrigerant in a liquid state. When first refrigerant with relativelylow boiling temperature is used for main refrigeration cycle 205, thetemperature of the liquid refrigerant is relatively low and thetemperature span between the highest and lowest temperature is wider. Byselectively opening valve 300, a variety or span of temperatures betweenthe two extreme temperatures may be controllably reached. Controller 10may control operation of both auxiliary refrigeration cycle 210 and mainrefrigeration cycle 205 to obtain a desired temperature and cooling rateat evaporator 70.

Reference is now made to FIG. 7 showing a simplified block diagram of anexample single loop refrigeration cycle operated with a plurality ofseparately controlled evaporators in accordance with some exampleembodiments. According to some example embodiments, a same refrigerationcycle may be operated to separately cool a plurality of different bodiesand volumes or different spaces. According to some example embodiments,refrigeration cycle 150 is similar to operation to refrigeration cycle100 (FIG. 1) with the addition of a multiple evaporators, e.g.evaporator 71, 72 and 79, each of which may be separately controlled.Refrigeration cycle 150 together with controller 10 form an examplecooling system. Sensors 90 when present may also be part of the coolingsystem. In some example embodiments, each evaporator may receivebi-phase refrigerant flow from a dedicated mixing chamber, e.g. mixingchamber 401, 402 and 409 and dedicated metering device, e.g. meteringdevice 61, 62 and 69. Each dedicated mixing chamber, e.g. mixing chamber401, 402 and 409 is associated with a dedicated valve, e.g. valve 301,302 and 309 configured to selectively regulate gas flow rate from acommon compressor 30 into its mixing chamber.

Optionally, liquid refrigerant in main flow path 314 may freely flowinto each of the dedicated mixing chambers. In this manner eachevaporator may provide cooling at a different rate and temperature. Insome example embodiments, dedicated sensors, e.g. sensors 91, 92, and 99may provide input for regulating each of the evaporators. Optionally,controller 10 is configured to control operation of refrigeration cycle150 including separately controlling each of valves 301, 302 and 309. Insome example embodiments output from each of the evaporators may besuctioned by a single accumulator 20 and compressed by a same compressor30 and condensed by a same condenser 40 and optionally dryer 50.According to some example embodiments, compressor 30 is configured to beoperated at a constant rate while providing different levels of coolingat each evaporator. In alternate example embodiments, when a singlevalve 300 and single mixing chamber 400 may feed a portion of theevaporators. In yet other example embodiments, a refrigerant cycle mayinclude a plurality of groups of evaporators, with evaporators in a samegroup being commonly controlled and evaporators in different groupsbeing separately controlled.

Reference is now made to FIG. 8 showing a simplified block diagram of anexample double loop refrigeration cycle operated with a plurality ofseparately controlled evaporators in accordance with some exampleembodiments. According to some example embodiments, refrigeration cycle250 may be similar to refrigeration cycle 205 with the addition ofmultiple evaporators, e.g. evaporators 71, 72 and 79 each of which maybe separately controlled. Refrigeration cycle 250 together withcontroller 10 form an example cooling system. Sensors 90 when presentmay also be part of the cooling system. As explained in reference toFIG. 8 that similarly shows a plurality of separately controlledevaporators, each evaporator may receive bi-phase refrigerant flow froma dedicated mixing chamber, e.g. mixing chamber 401, 402 and 409 anddedicated metering device, e.g. metering device 61, 62 and 69. Accordingto some example embodiments, each dedicated mixing chamber, e.g. mixingchamber 401, 402 and 409 is associated with a dedicated valve, e.g.valve 301, 302 and 309 configured to selectively regulate gas flow rateinto its mixing chamber. Optionally, liquid refrigerant in main flowpath 314 may freely flow into each of the dedicated mixing chambers. Insome example embodiments, dedicate sensors, e.g. sensors 91, 92, and 99may provide input for regulating each of the evaporators. Optionally,controller 10 is configured to control operation of refrigeration cycle150 including separately controlling each of valves 301, 302 and 309. Insome example embodiments output from each of the evaporators may besuctioned by a single accumulator 20 and compressed by a same compressor30 and condensed by a same heat exchanger 80. Optionally, thevapor-liquid separator may also be common to each of the flow pathsreach the different evaporators. In alternate example embodiments, whenseparate control is not required, a refrigeration cycle may include asingle valve 300 and single mixing chamber 400 that is configured tofeed a plurality of evaporators. In yet other example embodiments, arefrigeration cycle may include a plurality of groups of evaporatorswith evaporators in a same group being commonly controlled andevaporators in different groups being separately controlled.

Reference is now made to FIG. 9 showing a simplified flow chart of anexample method to regulate temperature in accordance with some exampleembodiments. According to some example embodiments, a cooling commandsuch as a desired temperature and/or a desired cooling rate may bedefined by a user or by a computer based on temperature sensing (block510). In order to achieve the selected cooling parameter, a separateflow path for gas and liquid refrigerant is established (block 520). Insome example embodiments, separate flow paths may be achieved byseparating a bi-phase mixture of refrigerant, e.g. with a vapor-liquidseparator emerging from a compressor. In other example embodiments, theseparate flow paths may be achieved by directing only a portion ofgaseous flow emerging from the compressor to a heat exchanger or acondenser to condense into a liquid while diverting a remainder of thegaseous flow through a separate flow path that does not undergocondensation. According to some example embodiments, the separated flowis combined in a selected proportion (block 530). According to someexample embodiments, the flow is combined in a dedicated mixing chamberand the selected proportion is achieved with a valve controlling flow ofgas phase into the mixing chamber. The combined or mixed flow may thenbe fed into an evaporator (block 540). According to some exampleembodiments, the selected proportion determines temperature of bi-phaserefrigerant entering an evaporator as well as a proportion of liquidrefrigerant in the evaporator. Temperature and other cooling parametersmay be monitored with one or more sensors (block 550) and output fromthe sensors may be applied for dynamically updating the coolingparameters defined (block 510). The present inventors have found thatthe cooling methods as described herein provides for improvedtemperature regulation. Optionally, a selected temperature may bemaintained with an accuracy of 0.5° C. According to some exampleembodiments, operation of the cooling system does not require alteringoperation of the compressor and therefore the compressor may be operatedat a constant steady state rate that is selected for with considerationof power efficiency. Furthermore, by operating the compressor at aconstant steady state rate, the noise level may be reduced as comparedto systems that require turning the compressor ON/OFF during itsoperation.

Reference is now made to FIG. 10 showing a perspective view of anexample temperature forcing system with an example double looprefrigeration cycle in accordance with some example embodiments.According to some example embodiments, a cooling system as describedherein may be a temperature forcing system for cooling semiconductorcomponents under test. Temperature forcing system 275 may be for examplea double loop refrigeration cycle similar to refrigeration cycle 200(FIG. 6). According to some example embodiments, an evaporator shown inFIG. 10 may be in the form of a plate or may be integrated in plate a71. Optionally, plate 71 is configured to be in physical contact withsemiconductor components under test. In some example embodiments, plate71 may also include a heating system that includes a heating element.Temperature forcing system may selectively operate one of refrigerationcycle 275 and heating system to test the semiconductor component indifferent extreme temperatures.

Reference is now made to FIGS. 11A, 11B and 11C showing three exampleconfigurations for integrating a heating coil on a temperature forcingplate in accordance with some example embodiments. In some exampleembodiments, a temperature forcing system for cooling semiconductorcomponents under test additionally includes a heating coil that isconfigured to heat the semiconductor component under test. In someexample embodiments, temperature forcing plate 71 is thermally coupledto both an evaporator 70 for cooling as well as a heating coil 600 forheating. The heating coil 600 may optionally be overlaid aboveevaporator 70 with the evaporator 70 being closest to the componentbeing tested as shown in FIG. 11A, overlaid on a bottom of evaporator 70as shown in FIG. 11B or may be sandwiched between evaporator 70 and acontrol plate 700 (FIG. 11C). Flow 68 in evaporator 70 via capillarytube 60 and flow 72 out of evaporator 70 may be from above distal to thecomponent being tested. According to some example embodiments,controller 10 as described herein is additionally configured to controloperation of heating coil. In some example embodiments, controller 10 isconfigured to operate the cooling system with substantially only gas inthe evaporator while activating heating coil 700. Optionally, one ormore temperature sensors 90 are configured to provide feedback tocontroller 10 based on which operation of both the cooling and heatingmay be adjusted.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements. In addition, any priority document(s) of this applicationis/are hereby incorporated herein by reference in its/their entirety.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting. In addition, any priority document(s) of this applicationis/are hereby incorporated herein by reference in its/their entirety.

1. A method for cooling with a refrigerant based cooling system, themethod comprising: circulating a refrigerant in a main flow path of arefrigeration cycle including an accumulator, compressor, condenser andan evaporator; diverting a portion of flow to a bypass flow path from alocation along the main flow path that is downstream the compressor andupstream the condenser, wherein the portion of flow that is diverted tothe bypass flow path is flow of the refrigerant in a gaseous phase;dynamically controlling rate of flow through the bypass flow path; andcombining refrigerant in a gaseous phase flowing through the bypass flowpath with liquid only refrigerant flowing through the main flow pathdownstream the condenser and upstream from the evaporator.
 2. The methodof claim 1, wherein the combining of the refrigerant in a gaseous phaseand the liquid refrigerant is in a dedicated mixing chamber, wherein themixing chamber is integrated in the main flow path downstream from thecondenser and upstream from the evaporator.
 3. (canceled)
 4. The methodof claim 1, wherein the refrigerant upstream from the bypass flow pathis bi-phasic refrigerant and wherein the method further comprises:separating a liquid refrigerant from a vaporized refrigerant; directingthe liquid refrigerant to the condenser via the main flow path; anddiverting at least a portion of the vaporized refrigerant to the bypassflow path.
 5. The method of claim 1, wherein the refrigerant upstreamfrom the bypass flow path is fully vaporized.
 6. The method of claim 1,comprising sensing a cooling effect of the cooling system and adjustingthe rate of refrigerant flow through the bypass flow path based on thecooling effect that is sensed.
 7. The method of claim 1, comprisingcooling refrigerant flowing through the condenser based on heat exchangewith a second refrigeration cycle that is thermally coupled with thecondenser.
 8. The method of claim 1, wherein the main flow path isconfigured to branch out into a plurality of sub-flow paths downstreamfrom the condenser, and wherein refrigerant flowing in each of theplurality sub-flow paths feeds into one of a plurality of evaporatorsand wherein the refrigerant flowing in the plurality of evaporators iscollected by the accumulator.
 9. The method of claim 8, wherein thebypass flow path is configured to branch out into a plurality ofsub-bypass flow paths, wherein flow rate of refrigerant though each ofthe plurality of sub-bypass flow paths is separately controlled, whereinvaporized refrigerant from each of the plurality of sub-bypass flowpaths is combined with liquid refrigerant in one of the plurality ofsub-flow paths of the main flow path.
 10. A cooling system comprising: arefrigerant; an accumulator, a compressor, a condenser and an evaporatorfluidly connected by a main flow path configured to circulaterefrigerant therein; a bypass flow path configured to divert a portionof flow from a location on the main flow path that is downstream thecompressor and upstream the condenser, wherein the portion of flow thatis diverted to the bypass flow path is flow of the refrigerant in agaseous phase; a valve configured to control flow through the bypassflow path; a mixing chamber configured to receive only liquidrefrigerant from the main flow path and to receive the refrigerant inthe gaseous phase from the bypass flow path and to direct outflow fromthe mixing chamber to the evaporator; and a controller configured todynamically control operation of the valve.
 11. The cooling system ofclaim 10, wherein the mixing chamber comprises: a first inlet configuredto receive flow from a location along the main flow path that isdownstream the condenser and upstream from the evaporator; a secondinlet configured to receive flow from the bypass flow path; and anoutlet configured to direct flow from one or more of the first inlet andthe second inlet to the evaporator.
 12. The cooling system of claim 10,wherein outflow from the mixing chamber is through a tube including anopen tip penetrating within the mixing chamber, wherein the tip ispositioned at a defined height within the mixing chamber.
 13. Thecooling system of claim 12, wherein the tube is integral to a meteringdevice providing flow communication between the mixing chamber and theevaporator.
 14. The cooling system of claim 12, wherein the tube is acapillary tube.
 15. The cooling system of claim 11, wherein the mixingchamber is elongated in a vertical direction and wherein the first inletis positioned below the second inlet.
 16. The cooling system of claim10, wherein the portion of flow through the bypass flow path is gaseousflow.
 17. The cooling system of claim 10, comprising a vapor-liquidseparator integrated into the main flow path downstream from thecompressor and configured to direct flow to the bypass flow path,wherein the vapor-liquid separator is configured to receive bi-phaserefrigerant from the compressor and to separately direct liquidrefrigerant to the condenser and at least a portion of the vaporizedrefrigerant to the bypass flow path.
 18. The cooling system of claim 10,comprising a flow splitter configured to divide outflow from thecompressor between the main flow path and the bypass flow path, whereinthe refrigerant upstream the flow splitter is fully vaporized.
 19. Thecooling system of claim 10, comprising a sensor configured to sense acooling effect of the cooling system, wherein the controller isconfigured to receive input from the sensor and to regulate the valvebased on the input.
 20. The cooling system of claim 10, comprising anadditional refrigeration cycle separate from the main flow path andthermally coupled to the condenser, wherein the additional refrigerationcycle is configured cool refrigerant in the main flow path.
 21. Thecooling system of claim 10 comprising a plurality of evaporators andwherein refrigerant from the plurality of evaporators is collected bythe accumulator.
 22. The cooling system of claim 21, comprising: aplurality of sub-bypass flow paths, each branching out from the bypassflow path; a plurality of valves, each of the plurality of valvesconfigured to control flow through one of the plurality of sub-bypassflow paths; and a plurality of mixing chambers, each of the plurality ofmixing chambers configured to receive refrigerant from both the mainflow path and one of the plurality of sub-bypass flow path and to directoutflow from the mixing chamber to one of the plurality of evaporators.23. The cooling system of claim 22, wherein the controller is configuredto separately control each of the plurality of valves and comprising aplurality of sensors, each configured to sense a cooling effect based onone of the plurality of evaporators, wherein the controller isconfigured to regulate the plurality of valves based on input from theplurality of sensors.
 24. A mixing chamber integrated in a refrigerationcycle, the mixing chamber comprising: a housing having an elongatedshape along a vertical direction; a first inlet configured to receivecondensed liquid refrigerant only from a main flow path of arefrigeration cycle; a second inlet configured to receive vaporizedrefrigerant expelled from a compressor of the refrigeration cycle; andan outlet port configured to direct flow from one or more of the firstinlet and the second inlet to an evaporator of the refrigeration cycle.25. The mixing chamber of claim 24 comprising: a tube extending throughthe outlet and configured to extend vertically within the housing at adefined height, wherein flow out of the chamber is configured to flowthrough the tube.
 26. The mixing chamber of claim 25, wherein the tubeextends out of the mixing chamber and is integral to a metering deviceof the refrigeration cycle.
 27. The mixing chamber of claim 25, whereinthe tube is a capillary tube.
 28. The mixing chamber of claim 25,wherein an open end of the tube within the mixing chamber is at leastone of: angled, perforated and covered with a porous material.
 29. Themixing chamber of claim 24, wherein the first inlet is positioned belowthe second inlet.
 30. The mixing chamber of claim 24, wherein the outletis through a floor or base of the housing.